Everyone's talking about Greta Gerwig, Saoirse Ronan, and Laurie Metcalf, but Beanie Feldstein manages to steal "Lady Bird" right out from under them.

Beanie Feldstein might be the younger sister of Jonah Hill, but after “Lady Bird,” she doesn’t need a famous relative to make her name stand out. Currently holding her own opposite Bette Midler on Broadway’s “Hello, Dolly!” while “Lady Bird” breaks box office records, Feldstein — who plays the best friend to the movie’s wayward teen, played by Saoirse Ronan — may be the year’s most exciting discovery.

With all due respect to the brilliant cast of “Lady Bird,” if a 23-year-old relative unknown can hold her own against Bette Midler, the rest of the world doesn’t stand a chance. Greta Gerwig’s fine-tuned directorial has been called “beautiful,” “insightful,” and “perfection”—and that’s just by New York Times film critic A.O. Scott. The movie is led by a winsome Ronan and fiercely commanding Laurie Metcalf, but Feldstein’s talent is established over the course of the movie.

Playing Lady Bird’s (Ronan) stubbornly sincere best friend Julie, Feldstein steals every scene in which she appears, whether by sweetly stammering to the cool young math teacher, or belting out “Crash” by Dave Matthews Band in one of the best nostalgia-tinged moments in recent American movies. Cherubic-faced with killer comic timing, Feldstein is at once a refreshing and familiar onscreen presence, breathing just enough sass and warmth into Julie that you half expect her to become your new best friend. Luckily, Feldstein wants that, too.

“I love to be the best friend,” Feldstein told IndieWire in a recent interview, pausing for emphasis. “It’s like my dream in life to be everybody’s best friend.” She balks at conventional industry wisdom that one should be careful not to get typecast in such roles. “I’ve heard people say ‘you don’t wanna play the best friend, you want to play the girl.’ Julie is Lady Bird’s best friend, but that is made to be special and sacred and loving and full. That’s all Greta, she gives every character their due in a very special way.”

According to Feldstein, Gerwig “felt like a big sister or a mom in some ways.” Between Ronan, Gerwig, and herself, she added, “We felt like this gaggle of sisters that were creating this thing that really mattered to us.” She desperately wanted to deliver for Gerwig, and described the joy of hearing the director “cackling” in the background during particularly funny scenes, like the one where Lady Bird and Julie break into the communion wafers. “It really felt like we were doing something right.”

“Lady Bird” hits all the beats of a satisfying coming-of-age story while avoiding every potential pitfall of the now-ubiquitous genre. That’s because Gerwig, once a teenage girl herself, knows friendship is a girl’s first romance. “The love story is between Julie and Lady Bird, and Lady Bird and her mom,” said Feldstein. “Falling in and out of love with each other, or realizing how much they matter to each other.”

Beanie Feldstein and Saoirse Ronan.

A24

Ever the devoted best friend, Julie accepts Lady Bird back with open arms after her brief stint with the popular kids proves unfulfilling. “When Lady Bird comes back to Julie, it’s this sweeping romantic moment that would normally happen between a guy and a girl. In our movie, it’s between two best friends, and I think that’s really cool and sweet. You can be really romantic and put a lot of effort into friendship.”

Julie’s schoolgirl crush on her teacher, Mr. Bruno, remains innocent where many other films might push towards more tawdry ends. Upon first viewing, Feldstein was surprised to hear the audience laugh at Julie’s vulnerable moment. “I was sitting there baffled that it was getting laughs, because as Julie I just loved him. Of course, objectively I can be like, ‘Oh, that’s hilarious.'”

She also finds humor in sincerity as Nora, her scene-stealing turn in “Neighbors 2” as a sorority girl gone wild. Nora’s first joint ends in a comically long coughing fit, and the mere sight of Feldstein sobbing in a pink polka-dotted onesie next to Zac Efron sells the entire scene. More than Julie, Nora’s broad comedic appeal is reminiscent of the kinds of roles that made her brother a household name. The comedy resemblance is strong, even if the family one isn’t, but Feldstein said she and Hill don’t talk much about acting. “I do, but just in the way you would talk to your sibling about work. We talk about work, but we have more heart to hearts than we talk about work.”

Read More:National Board of Review 2017 Winners: ‘The Post’ Named Best Film, Greta Gerwig is Best DirectorDespite earning big laughs from a supporting role in “Neighbors 2,” not to mention from the tiniest cutaways in “Lady Bird,” Feldstein said she doesn’t think of herself as a funny person. “I think I’m just around so many people who are naturally so funny.” The same goes for Julie: “I never thought of Julie as funny, which I think is maybe why she might be funny. In her brain she’s not funny at all, she’s just deeply sincere.”

Like Julie, every character in “Lady Bird” brims with a rich inner life; a testament not only to Gerwig’s writing and direction, but her casting, too. Ronan and Metcalf crackle with natural mother-daughter friction, and Stephen Henderson and Lois Smith instill their scenes with warmth and wisdom. Among Gerwig’s many inspired choices, however, Feldstein is the director’s biggest discovery.

“It’s very special to be in something that you genuinely think would be your favorite thing if you weren’t in it,” she said, beaming. “I’ll never get over it.”